1. Field of the Invention
The present invention relates generally to a significant improvement in cable-wrapped fiberglass reinforced plastic tanks adapted to store a contained fluid, and more particularly to an improved expansible bottom structure for permitting the side wall of the tank to expand radially outwardly under hydrostatic load.
2. Description of the Prior Art
U.S. Pat. No. 3,025,992 discloses a basic fiberglass reinforced plastic (FRP) tank wherein a steel cable is helically wound around the FRP side wall of the tank to absorb the hoop stress produced by a head of stored fluid.
U.S. patent application Ser. No. 448,669, filed Mar. 6, 1974, discloses two improvements in such cable-wrapped FRP tanks. The first improvement provides a unique top ring girder adapted to resist deformation of an upper portion of the side wall structure, when the tank is empty, due to wind loading. The second improvement provides a unique bottom ring girder designed to slide relative to a supporting foundation, and to resist an overturning moment applied to the tank.